Modellazione numerica di motore ottico ad accensione spontanea con miscele di combustibili

Una soluzione di semplice attuazione per l’abbattimento delle emissioni inquinanti nei motori ad accensione spontanea, è l’utilizzo di miscele di combustibili con differente numero di cetano. L’Istituto Motori di Napoli ha realizzato esperimenti su un motore ottico con una miscela di gasolio (80%) e benzina (20%), chiamata G20. L’effetto della benzina è di aumentare il ritardo all’accensione e perciò di prolungare il tempo di miscelamento pre-combustione con conseguente riduzione simultanea di NOx e particolato. Gli obiettivi di questa tesi sono la modellazione numerica del motore ottico presente al’Istituto Motori attraverso il codice CFD AVL FIRE e la simulazione di combustioni con miscele di combustibili. A solution of simple implementation to reduce pollutant emissions in compression-ignition engines, is the use of a blend of fuels with different cetane number. The Istituto Motori of Napoli has carried out tests with an optical engine using a mixture of diesel fuel (80%) and gasoline (20%), called G20. The effect of gasoline is to increase the ignition delay and thus to protract the time of pre-combustion, with consequent simultaneous reduction of NOx and soot. The aims of this thesis are numerical modelling, by means of the CFD AVL FIRE code, of the optical engine located at the Istituto Motori and numerical predictions of fuel mixture combustion

Numerical and experimental investigation of a piston thermal barrier coating for an automotive diesel engine application

This paper investigates the potential of coated pistons in reducing fuel consumption and pollutant emissions of a 1.6l automotive diesel engine. After a literary review on the state-of-the-art of the materials used as Thermal Barrier Coatings for automotive engine applications, anodized aluminum has been selected as the most promising one. In particular, it presents very low thermal conductivity and heat capacity which ensure a high “wall temperature swing” property. Afterwards, a numerical analysis by utilizing a one-dimensional Computational Fluid Dynamics engine simulation code has been carried out to investigate the potential of the anodized aluminum as piston Thermal Barrier Coating. The simulations have highlighted the potential of achieving up to about 1% in Indicated Specific Fuel Consumption and 6% in heat transfer reduction. To confirm the simulation results, the coated piston technology has been experimentally evaluated on a prototype engine and compared to the baseline aluminum pistons. Despite the promising potential for Indicated Specific Fuel Consumption reduction highlighted by the numerical simulation, the experimental campaign has indicated a slight worsening of the engine efficiency (up to 2% at lower load and speed) due to the slowdown of the combustion process. The primary cause of these inefficiencies is attributed to the roughness of the coating

Numerical Investigation on the Effects of Different Thermal Insulation Strategies for a Passenger Car Diesel Engine

AbstractOne of the key technologies for the improvement of the diesel engine thermal efficiency is the reduction of the engine heat transfer through the thermal insulation of the combustion chamber. This paper presents a numerical investigation on the effects of the combustion chamber insulation on the heat transfer, thermal efficiency and exhaust temperatures of a 1.6 l passenger car, turbo-charged diesel engine. First, the complete insulation of the engine components, like pistons, liner, firedeck and valves, has been simulated. This analysis has showed that the piston is the component with the greatest potential for the in-cylinder heat transfer reduction and for Brake Specific Fuel Consumption (BSFC) reduction, followed by firedeck, liner and valves. Afterwards, the study has been focused on the impact of different piston Thermal Barrier Coatings (TBCs) on heat transfer, performance and wall temperatures. This analysis has been performed using a 1-D engine simulation code coupled with a lumped mass thermal model, representing the engine structure. A time-periodic wall conduction model has been used to calculate the wall temperature swings along the combustion chamber surface and within the engine cycle. Two different TBC materials, Yttria-Partially Stabilized Zirconia (Y-PSZ) and anodized aluminum, and different layer thicknesses have been simulated